Adult male Antarctic fur seals: tourists, trouble makers or marine ecosystem sentinels?

Resource competition often results in mechanisms that ameliorate its effects, typically through the partitioning of resource exploitation either temporally or spatially.  Understanding the spatial and temporal overlap between predators that exploit the same resource then is fundamental to understanding the impacts one predator can have on another.  The fishery for Antarctic krill operates along the west Antarctic Peninsula and the Scotia Sea, and while there are calls for its expansion there is a concern that any increase in catch levels should not result in long-lasting or irreparable damage to the ecosystem.  Considering the fishery as another krill predator then, it follows that understanding how it functionally overlaps with other krill predators such as seals, whales and seabirds is critical.  Similarly, characterizing the competitive interactions between these species is key to disentangling the drivers of functional responses of each species.  We highlight this by collecting at-sea habitat use of adult male Antarctic fur seals which move into the Bransfield Strait and southern Scotia Sea during the austral summer and remain there throughout the winter. We identify considerable spatial and temporal overlap with breeding Chinstrap penguins in the Bransfield Strait at a time when fishing effort is minimal, as well as when effort is at is maximum at the South Orkney Islands. We recommend that this overlap should be considered in understanding the functional response of penguins and suggest that male AFS could be a useful monitoring taxon given its lack of post-breeding spatial constraint, its numerical abundance and the relative ease by which data could be collected.